Patent GB-1069895-A (GB)
Title: Improvements in liquid springs
IPC: F16J15/32
Filed: 1964-05-12
Abstract: 1,069,895. Liquid springs; seals. TAYCO DEVELOPMENTS Inc. May 12, 1964 [May 13, 1963], No. 19704/64. Headings F2B and F2S. A liquid spring 20 comprising a piston rod 30 with a piston 40 which works in a tapered cylinder wall 23A has a long-path plastics seal 50 made e.g. of nylon or similar flowable plastics material, the seal having a central portion which is an interference fit with with cylinder wall 23A and the rod 30 so that the cylinder is slightly deformed by the interference fit, an end groove 53 providing two radially elastic sealing lips 56, 57, and a conical base 68 which cooperates with a corresponding face on an end closure member 69 screwed into the adjacent end of the cylinder 23. The plastics of the seal can flow into a cavity 65 between the rod 30 and the closure member 69 to provide a bearing for side loads on the piston rod 30 which, for minimum wear of the seal, should be finished during production by longitudinal working of the rod. During a compression stroke spring liquid flows through the annular space between the piston 40 and the cylinder 23, which space becomes progressively narrower, into an annular groove 47, and through ports 43 leading to the cylinder space behind the piston. At the end of the stroke a metering probe 41 on the piston 40 enters a metering ring 24b screwed into the inner end of an externally threaded cylinder extension 24. A yieldable split metallic, or solid plastics, piston ring 44 seals the piston 40 against the cylinder wall 23A. The rod 30 has a refilling or servicing bore 31 which terminates in a smaller bore 33 which is closed by a valve seal 32 carried by a threaded spigot 49 on the piston 40. Damping may be carried out by means of a plurality of holes through the piston, the size of the holes being progressively reduced by the ring 44 when the latter is radially contracted as it travels down the taper 23A. In a modification, Fig. 4 (not shown), the piston 40 is replaced by a collar (440) which is riveted to the rod (430) and which has a seal-engaging stop (447). An anti-extrusion collar (451), of high strength plastics or bearing alloy, prevents loss of seal material (450). The preload of the spring can be increased by forming an indentation (490) in the end of the cylinder extension (480). In a further modification, Fig. 5 (not shown), the piston (140), provided with through ports (143), carries a skirt (141) which slidingly engages a cylinder (125) screwed into the seal (150) between two elongated lips (156), (157), and the end closure (160) is provided with an epoxy resin seal (12111), Fig. 6a (not shown), and a cylindrical extension (161). In another arrangement, Fig. 7 (not shown), a composite seal comprises outer and inner wedge-shaped members (251), (252). According to the arrangement of Fig. 8 (not shown), the seal (350) having no lips such as 56, 57, as shown, is provided with an O ring elastomeric seal (352). In the arrangement of Fig. 10 (not shown) a filler cap (300) for charging the spring has a bore (301) which houses a plastics guide seal (302) to receive a piston rod (230) the passage (431) through which communicates with a liquid supply nozzle (270). In an alternative embodiment, Fig. 14 (not shown), an upstanding shoulder (667) on a cap member (668), which retains the seal (650), co-operates with the piston (640) to take the high pre-load instead of the seal (650). Alternatively a preload abutment device may comprise a ring retained on an inwardly-directed circular rib in the inner face of the cylinder, or a tubular stop member, which is threaded into the cylinder extension, slidingly receives the piston, and has a number of orifices for the passage of liquid.